Process for the simultaneous desulfurization and coking of a residual petroleum fraction



Jan. 17, 1961 A H. SCHUTTE 2,968,611

PROCESS FOR THE SiMULTANEOUS DESULFURIZATION AND COKING OF A RESIDUAL PETROLEUM FRACTION Filed D60. 12, 1955 fiesulf'uriziry 44M INVENTOR @NEY United States Patent O PROCESS FOR THE SIMULTANEOUS DESULFURE- ZATION AND COKING OF A RESIDUAL PETRO- LEUM FRACTION August H. Schutte, Hastings on Hudson, N.Y., assignor to The Lummus Company, New York, N.Y., a corporation of Delaware Filed Dec. 12, 1955, Ser. No. 552,657

5 Claims. (Cl. 208-126) The present invention is directed to a process for the continuous thermal conversion of heavy liquid hydrocarbons having a high sulfur content into hydrocarbon vapors and dry coke while simultaneously removing sulfur therefrom by a desulfurizing reaction and this application is a continuation-in-part of my copending application Serial Number 327,984, filed December 26, 1952, and entitled Process of Desulfurization, now abandoned.

Previous attempts to desulfurize heavy oils have been limited because such operations involve the decomposition of large quantities of carbon thus requiring removal from the catalyst by regeneration procedures similar to those used in catalytic cracking. The cost of the regeneration of heavily coked catalyst was therefore prohibitive.

It has been observed that in the continuous contact coking processes of A. H. Schutte et al. Patents No. 2,561,334 and 2,600,078 as now practiced the sulfur pres: ent in the residual oil charge stock is distributed throughout all the products from gas to coke.

I have now discovered that the sulfur content of heavy oils can be economically removed for ultimate recovery by adaptation of my present invention to the principles of my above-mentioned patents. The latter of these patents discloses the details of a process of making free-flowing coke pebbles in which heavy hydrocarbon stocks in liquid phase are repeatedly applied to coke nuclei, with conversion to dry coke layers and reheating of the coked particles without burning between successive applications of liquid phase hydrocarbons. By using an inexpensive desnlfurization agent on a once-through basis, thermal conversion of the heavy hydrocarbon oils to lighter hydrocarbon vapors, coke pebbles of desired size, and removal of sulfur are accomplished simultaneously. The desulfurizing agent will appear as ash in the coke product. When the coke product is to be used for making metallic electrodes, an agent having a composition compatible with such end use may be chosen.

It is the principal object of this invention to provide a process for desulfurizing heavy hydrocarbons while conducting a continuous contact coking operation.

A further object of this invention is to employ, in the process described, a desulfurization agent suitable for application to contact coke particles receiving liquid heavy hydrocarbon charge for thermal conversion to dry coke.

An additional inventive object is to provide simple and efficient procedures for applying the desulfurization agent to the coke particles.

These and other features of improvement will be more fully understood from the following detailed description of preferred embodiments of the invention, when taken in connection with the accompanying drawing, in which:

Figure l is a schematic diagram of apparatus illustrating one manner in which the process can be performed continuously.

Figure 2 is a schematic diagram of apparatus illustrating a second embodiment in which the process can be performed continuously.

2,968,611 Patented Jan. 17, 1961 Referring to Figure 1, a heavy hydrocarbon charge in liquid phase is fed through line 10, mixed with desulfurizing agent supplied through line 30* and the mixture preferably heated in the tubular heater 29. In this heater considerably desulfurization will normally be obtained, followed by a completion of this reaction and a coking of the oil upon introduction of the mixture into the hot coke stream entering reactor 12. The coke produced from the oil feed plus the desulfurizing agent will be deposited in the particles of circulating coke. The hydrocarbon vapor product and any hydrogen sulfide from the desulfurization reaction are disengaged from the solids and removed from the reactor, as at 14.

At the bottom of the reactor 12 substantially dry, coated coke particles or pebbles flow freely through a discharge line 16 to the lower end of a closed elevator line 18. A coke pebble drawoif line 20 is provided intermediate the discharge line for removal of net coke product as pebbles. The removal may be on a continuous or intermittent basis to maintain a substantially constant inventory.

Suitable elevating means (not shown) acting within line 18 carries the partially cooled coke pebbles to a point above a heater 22, for recycling thereto through a downwardly extending line 24.

In the heater 22 the coke particles are reheated to a temperature suitable for readmission to the reaction Zone in reactor 12. The pebbles or particles may be heated in any suitable manner in heater 22. Where the contact process is being conducted for the purpose of producing high density, substantially impervious and homogeneous pebbles for heat exchange operations or the like, the reheating in heater 22 will be non-combustive. Figure 1 illustrates one manner in which hot gases may be passed upwardly through the downwardly moving portion of the gravity-packed coke particle column in heater 22, the gas for heating being admitted through a bottom line 25 and removed as stack gases through a top line 26.

The reheated coke particles pass downwardly solely by gravity from the bottom of heater 22 to the top of reactor 12 through a short connecting line 28, the column of particles being continuously moved by gravity through the heater 22 and through the reactor 12.

Suitable desulfurizing agents for use in the process are well known in the art. Examples would be aluminum hydrate, boron oxide, iron oxide, clays, bauxite, etc. Some of the well known materials of this type convert the hydrocarbon sulfur compounds into H 8 and some of them eliminate the sulfur as a deposit on the solids leaving the reactor. The process is obviously operable in either way.

If desirable, the desulfurizing agent may be mixed with or applied to the circulating coke upstream of the oil charge point, as illustrated in Figure 2, instead of being mixed with the oil prior to its entry into the reactor, as illustrated in Figure 1.

Referring to Figure 2, this figure illustrates a process quite similar to the process as illustrated in Figure 1, wherein the desulfurizing agent is mixed with or applied to the circulating coke upstream of the oil charge. The same numerals as used in Figure 1 are applied to like parts and like streams. In Figure 2, the coke particles are reheated in heater 22 to a temperature suitable for readmission to the reaction zone in reactor 12. The heated coke particles are coated with a desulfurization agent introduced through line 30'. These coated coke particles are then substantially uniformly coated with heated liquid hydrocarbons introduced through line 10, the liquid hydrocarbons being preheated in heater 29. The coke particles, coated with both the desulfurization agent and the liquid hydrocarbons are then introduced into reactor 12 wherein a simultaneous desulfurizing and coking reaction occurs. The products are removed as in the process illustrated in Figure 1.

Where my process is started with coke nucleus particles that have been saturated and become impervious, such particles or pebbles may be of a small order of size. By recycling and successive application of coke coatings these pebbles may be permitted to grow to a much larger size, say of the order of one-quarter inch to one and onehalf inch in major dimension. Each application of oil for coke coating will be accompanied by a deposition of desulfurizing agent. A residence time of 5 to 40 minutes in reactor 12 is appropriate.

The coke particles entering the reaction zone are preheated from about 850 F. to about 1100 F. for thermal conversion of the stock.

Preferably the charge oil temperature will be in the range of 700 F. to 900 F., depending on the specific nature of the oil. The feed oil comprises such heavy hydrocarbons as bottoms, heavy petroleum residues, and hydrocarbon residuals.

In accordance with the teachings of my patents, the ratio of oil feed to coke particles, and the temperatures of each will be mutually adjusted to produce substantially .dry, free flowing coke pebbles at the bottom of the reaction zone.

The aluminum hydrate or other desulfurizing agent will be so introduced as to be available for reaction at the top portion of the reaction zone. The desulfurization reaction is carried out in the absence of hydrogen.

The operating pressure in the reaction zone is relatively low, ranging from 2 to 60 p.s.i.g. according to the pressure required for subsequent treatment of the product vapors.

An example of the application of a heavy hydrocarbon having a high sulfur content to a continuously moving petroleum coke particle mass is as follows:

Charge-9.9 A.P.I.--Vacuum ResidualLos Angeles Basin Crude. Sulfur in charge1.73% by weight.

Particle material.-Dense petroleum (equilibrium) coke: Size: minimum to 1" maximum.

Desulfurizing agent.-Aluminum hydroxide (Al(OH) Prcedure.Five. (5) tons per day of desulfurizing agent is mixed with 5,000 bbls. per day of oil charge and heated in a tubular heater to approximately 795 F. The heated mixed charge is introduced to the coking chamber; through which gravity packed particle coke is passed. The particle inlet temperature above the charge point is 1040 F.

The particles in the coking chamber move downwardly from the feed point to the bottom of the conversion zone with the average particle residence time of approximately thirty (30) minutes to allow a full and complete conversion. The coke is removed as a free flowing homogeneous stream.

Analysis of the coke product indicates that the desulfurizing agent forms only approximately 5% ash by weight in the coke deposited and that the sulfur present in such coke is in the form of aluminum compounds.

Where continuous thermal conversion of the above charge was performed without simultaneous desulfurization analysis showed that the sulfur content in the products of conversion by weight amounted to:

Percent Gasoline (400 F. E.P.) 1.03 Gas oil (400-720 F. boiling point) 1.72 Coke 1.72

While there have been described preferred embodiments of the process of this invention, it is to be understood that modifications may be made therein without departing from the principles of the invention and the scope of the appended claims.

I claim:

1. A continuous process for'simultaneously coking and desulfurizing hydrocarbon residual oils having a high sulfur content in the presence of a moving gravity packed bed of heated coke particles which comprises: mixing aluminum hydrate as a desulfurizing agent with a stream of liquid hydrocarbon residual oils to be desulfurized and coked; heating said stream of liquid hydrocarbon residual oils including said desulfurizing agent to a temperature of from about 700 to 900 F.; introducing said heated stream of liquid hydrocarbon residual oils and desulfurizing agent into a moving gravity packed column of relatively hot coke particles whereby the particles of said column are substantially uniformly coated With said desulfurizing agent and said liquid hydrocarbon residual oils, said coke particles in said column being heated to a temperature of from about 850 to 1100 F.; passing the coated coke particles of said column as a gravity packed bed downwardly through a conversion zone without the introduction of hydrogen thereto; maintaining said coated coke particles in the conversion zone at the coking temperatures established by said heated particles and at a pressure of from 2 to 60 p.s.i.g. for

a period sufficient to coke said liquid hydrocarbon residual oils thereby to form light hydrocarbon vapors and a dry coke deposit on said particles, and to desulfurize said liquid hydrocarbon residual oils by converting sulfur therein to hydrogen sulfide; withdrawing coke particles having a substantially dry coke and spent aluminum hydrate deposit thereon from the lower portion of said conversion zone, a portion of said withdrawn coke'particles constituting product coke and the remaining portion of said withdrawn coke particles being reheated and returned to said moving gravity packed column; and removing said light hydrocarbon vapors and said hydrogen sulfide from the upper portion of said conversion zone.

2. A continuous process for simultaneously coking and desulfurizing hydrocarbon residual oils having a high sulfur content in the presence of a moving gravity packed bed of heated coke particles which comprises: coating the heated coke particles of a moving gravity packed column with an aluminum hydrate desulfurizing agent, said coke particles in said column being heated to a temperature of from about 850 to 1100 F.; heating a stream of liquid hydrocarbon residual oils to be desulfurized and coked to a temperature of from about 700 to 900 F. and introducing said stream into the moving gravity packed column of relatively hot coke particles whereby the particles of said column are substantially uniformly coated with said heated liquid hydrocarbon residual oils; passing the coated coke particles of said column as a gravity packed bed downwardly through a conversion zone without the introduction of hydrogen thereto; maintaining said coated coke particles in the conversion zone at the coking temperatures established by said heated particles and at a pressure of from 2 to 60 p.s.i.g. for a period sufiicient to coke said liquid hydrocarbon residual oils thereby to form light hydrocarbon vapors and a dry coke deposit on said particles, and to desulfurize said liquid hydrocarbon residual oils by converting sulfur therein to hydrogen sulfide; withdrawing coke particles having a substantially dry coke and spent aluminum hydrate deposit thereon from the lower portion of said conversion zone, a portion of said withdrawn coke particles constituting product coke and the remaining portion of said withdrawn coke particles being reheated and returned "to said moving gravity packed column; and removing said light hydrocarbon vapors and said hydrogen sulfide from the upper portion of said conversion zone.

3. A continuous process for simultaneously coking and desulfurizing residual petroleum stocks having a high sulfur content in the presence of a moving gravity packed bed of heated coke particles which comprises: introducing a desulfurizing agent effective to desulfurize residual petroleum stocks under coking conditions and liquid residual petroleum stocks to be desulfurized and coked into a moving gravity packed column of relatively hot coke particles whereby the particles of said column are substantially uniformly co; ted with said desulfurizing agent and said liquid residual petroleum stocks, said liquid residual petroleum stocks being preheated to a temperature of from about 700 to 900 F. and said coke particles in said column being heated to a temperature of from about 850 to 1100 F; passing the coated coke particles of said column as a gravity packed bed downwardly through a conversion zone without the introduction of hydrogen thereto; maintaining said coated coke particles in the conversion zone at the coking temperatures established by said heated particles and at a pressure of from 2 to 60 p.s.i.g. for a period suificient to coke said liquid residual petroleum stocks thereby to form light hydrocarbon vapors and a dry coke deposit on said particles, and to desulfurize said liquid hydrocarbons by reaction with said desulfurizing agent; withdrawing coke particles having a substantially dry coke and spent desulfurizing agent deposit thereon from the lower portion of said conversion zone, a portion of said withdrawn coke particles constituting product coke and the remaining portion of said withdrawn coke particles being reheated and returned to said moving gravity packed column; and removing said light hydrocarbon vapors and any gaseous desulfurization reaction products from the upper portion of said conversion zone.

4. A continuous process for simultaneously coking and desulfurizing residual petroleum stocks having a high sulfur content in the presence of a moving gravity packed bed of heated coke particles which comprises: mixing a desulfurizing agent efiective to desulfurize resid ual petroleum stocks under coking conditions with a stream of liquid residual petroleum stocks to be desulfurized and coked; heating said stream of liquid residual petroleum stocks including said desulfurizing agent to a temperature of from about 700 to 900 F.; introducing said heated stream of liquid residual petroleum stocks and desulfurizing agent into a moving gravity packed column of relatively hot coke particles whereby the particles of said column are substantially uniformly coated with said desulfurizing agent and said liquid residual petroleum stocks, said coke particles in said column being heated to a temperature of from about 850 to 1100 F.; passing the coated coke particles of said column as a gravity packed bed downwardly through a conversion zone without the introduction of hydrogen thereto; maintaining said coated coke particles in the conversion zone at the coking temperatures established by said heated particles and at a pressure of from 2 to 60 p.s.i.g. for a period sufficient to coke said liquid residual petroleum stocks thereby to form light hydrocarbon vapors and a dry coke deposit on said particles, and to desulfurize said liquid hydrocarbons by reaction with said desulfurizing agent; withdrawing coke particles having a substantially dry coke and spent desulfurizing agent deposit thereon from the lower portion of said conversion zone, a portion of said withdrawn coke particles constituting product coke and the remaining portion of said with drawn coke particles being reheated and returned to said moving gravity packed column; and removing said light hydrocarbon vapors and any gaseous desulfurization reaction products from the upper portion of said conversion zone.

5. A continuous process for simultaneusly coking and desulfurizing residual petroleum stocks having a high sulfur content in the presence of a moving gravity packed bed of heated coke particles which comprises: coating the heated coke particles of a moving gravity packed column with a desulfurizing agent effective to desulfurize residual petroleum stocks under coking conditions, said coke particles in said column being heated to a temperature of from about 850 to 1100 F.; heating a stream of liquid residual petroleum stocks to be desulfurized and coked to a temperature of from about 700 to 900 F. and introducing said stream into the moving gravity packed column of relatively hot coke particles whereby the particles of said column are substantially uniformly coated with said heated liquid residual petroleum stocks; passing the coated coke particles of said column as a gravity packed bed downwardly through a conversion zone without the introduction of hydrogen thereto; maintaining said coated coke particles in the conversion zone at the coking temperatures established by said heated particles and at a pressure of from 2 to p.s.i.g. for a period suflicient to coke said liquid residual petroleum stocks thereby to form light hydrocarbon vapors and a dry coke deposit on said particles, and to desulfurize said liquid residual petroleum stocks by reaction with said desulfurizing agent; withdrawing coke particles having a substantially dry coke and spent desulfurizing agent deposit thereon from the lower portion of said conversion zone, a portion of said Withdrawn coke particles constituting product coke and the remaining portion of said withdrawn coke particles being reheated and returned to said gravity packed column; and removing said light hydrocarbon vapors and any gaseous desulfurization reaction products from the upper portion of said conversion zone.

References Cited in the file of this patent UNITED STATES PATENTS 2,490,975 Mathy Dec. 13, 1949 2,534,025 Howes et a1 Dec. 12, 1950 2,561,334 Bowles et al. July 24, 1951 2,738,307 Beckberger Mar. 13, 1956 

1. A CONTINUOUS PROCESS FOR SIMULTANEOUSLY COKING AND DESULFURIZING HYDROCARBON RESIDUAL OILS HAVING A HIGH SULFUR CONTENT IN THE PRESENCE OF A MOVING GRAVITY PACKED BED OF HEATED COKE PARTICLES WHICH COMPRISES: MIXING ALUMINUM HYDRATE AS A DESULFURIZING AGENT WITH A STREAM OF LIQUID HYDROCARBON RESIDUAL OILS TO BE DESULFURIZED AND COKED, HEATING SAID STREAM OF LIQUID HYDROCARBON RESIDUAL OILS INCLUDING SAID DESULFURIZING AGENT TO A TEMPERATURE OF FROM ABOUT 700 TO 900*F., INTRODUCTING SAID HEAT STREAM OF LIQUID HYDROCARBON RESIDUAL OILS AND DESULFURIZING AGENT INTO A MOVING GRAVITY PACKED COLUMN OF RELATIVELY HOT COKE PARTICLES WHEREBY THE PARTICLES OF SAID COLUMN ARE SUBSTANTIALLY UNIFORMLY COATED WITH SAID DESULFURIZING AGENT AND SAID LIQUID HYDROCARBON RESIDUAL OILS, SAID COKE PARTICLES IN SAID COLUMN BEING HEATED TO A TEMPERATURE OF FROM ABOUT 850 TO 1100*F., PASSING THE COATED COKE PARTICLES OF SAID COLUMN AS A GRAVITY PACKED BED DOWNWARDLY THROUGH A CONVERSION ZONE WITHOUT THE INTRODUCTION OF HYDROGEN THERETO, MAINTAINING SAID COATED COKE PARTICLES IN THE CONVERSION ZONE AT THE COKING TEMPERATURES ESTABLISHED BY SAID HEATED PARTICLES AND AT A PRESSURE OF FROM 2 TO 60 P.S.I.G FOR A PERIOD SUFFICIENT TO COKE SAID LIQUID HYDROCARBON RESIDUAL OILS THEREBY TO FORM LIGHT HYDROCARBON VAPORS AND A DRY COKE DEPOSIT ON SAID PARTICLES, AND TO DESULFURIZE SAID LIQUID HYDROCARBON RESIDUAL OILS BY CONVERTING SULFUR THEREIN TO HYDROGEN SULFIDE, WITHDRAWING COKE PARTICLES HAVING A SUBSTANTIALLY DRY COKE AND SPENT ALUMINUM HYDRATE DEPOSITE THEREON FROM THE LOWER PORTION OF SAID CONVERSION ZONE, A PORTION OF SAID WITHDRAWN COKE PARTICLES CONSTITUTING PRODUCT COKE AND THE REMAINING PORTION OF SAID WITHDRAWN COKE PARTICLES BEING REHEATED AND RETURNED TO SAID MOVING GRAVITY PACKED COLUMN, AND REMOVING SAID LIGHT HYDROCARBON VAPORS AND SAID HYDROGEN SULFIDE FROM THE UPPER PORTION OF SAID CONVERSION ZONE. 